Alamannia or Alemannia was the territory inhabited by the GermanicAlemanni after they broke through the Roman limes in 213. The Alemanni expanded from the Main basin during the 3rd century, raiding the Roman provinces and settling on the left bank of the Rhine from the 4th century.

The Alamanni were pushed south from their original area of settlement in the Main basin and in the 5th and 6th century settled new territory on either side of the Rhine. Alemannia under Frankish rule later the Duchy of Swabia within the Holy Roman Empire covered a territory that was more or less undisputed during the 7th to 13th centuries, organised into counties or pagi.

Originally a loose confederation of unrelated tribes, the Alemanni underwent coalescence or ethnogenesis during the 3rd century, and were ruled by kings throughout the 4th and 5th centuries until 496, when they were defeated by Clovis I of the Franks at the Battle of Tolbiac.

The Alemanni during the Roman Empire period were divided into a number of cantons or goviae, each presided by a tribal king. But there appears to have been the custom of the individual kings uniting under the leadership of a single king in military expeditions.

Alemannian settlements on both sides of the Alps between the 3rd and 6th centuries.

Some kings of the Alemanni of the 4th and 5th centuries are known by name, the first being Chrocus (died 306), a military leader who organized raids across the limes during the 3rd century. Chnodomarius (fl. 350) supported Constantius II in the rebellion of Magnentius. Chnodomarius was the leader of the Alemannic army in the battle of Strasbourg in 357.

Macrian, Hariobaud, Urius, Ursicinus, Vadomar, and Vestralp were Alemannic kings who in 359 made treaties with Julian the Apostate. Macrian was deposed in an expedition ordered by Valentinian I in 370. Macrian appears to have been involved in building a large alliance of Alemannic tribes against Rome, which earned him the title of turbarum rex artifex ("king and crafter of unrest").

The Romans installed Fraomar as a successor of Marcian, but the Bucinobantes would not accept him and he was expelled and Macrian restored and Valentinian made the Bucinobantes his foederati in the war against the Franks. Macrian was killed on campaign against the Franks, in an ambush laid by the Frankish king Mallobaudes.

Gibuld (fl. 470) is the last known king of the Alemanni. His raid on Passau is mentioned in the vita of Saint Lupus. The name of Gibuld's successor who was defeated at Tolbiac is not known.

Though ruled by their own dukes, it is not likely that they were very often united under one duke in the 6th and 7th centuries. The Alemanni most frequently appear as auxiliaries in expeditions to Italy. The Duchy of Alsace was Alemannic, but it was ruled by a line of Frankish dukes and the region around the upper Danube and Neckar rivers was ruled by the Ahalolfing family and not by the ducal house which ruled central Alamannia around Lake Constance. Rhaetia too, though Alamannic, was ruled by the Victorids coterminously with the Diocese of Chur.

Alamannia was Christianised during the 7th century, although not as thoroughly[dubious– discuss] as either Francia to its west or Bavaria to its east. The first Alamannic law code, Pactus Alamannorum, dates to this period. The Roman dioceses of Strasbourg and Basel covered Alsace and that of Chur, as mentioned, Rhaetia. Alamannia itself only had a diocese in the east, at Augsburg (early 7th century). There were two Roman bishoprics, Windisch and Octodurum, which were moved early to other sites (Avenches and Sitten respectively).

Western Alamannia did eventually (7th century) receive a diocese (Constance) through the cooperation of the bishops of Chur and the Merovingian monarchs. The foundation of Constance is obscure, though it was the largest diocese in Germany throughout the Merovingian and early Carolingian era. The dioceses of Alamannia, including Chur, which had been a suffragan of the Archdiocese of Milan, were placed under the jurisdiction of the Archdiocese of Mainz by the Carolingians.

After the death of Dagobert I in 638, Alamannia, like Bavaria, Aquitaine, and Brittany, broke its ties with its Frankish sovereigns and struggled for independence. This was largely successful until the early 8th century, when a series of campaigns waged by the Arnulfingmayors of the palace reduced Alamannia to a province of Francia once again. It was, however, during this period of de facto independence that the Alamanni began to be ruled by one duke, though Alsace and Rhaetia remained outside of the scope of Alamannia.

Between 709 and 712, Pepin of Heristal fought against Lantfrid, who appears as dux of the Alamanni, and who committed to writing the second Alamannic law code, the Lex Alamannorum. In 743, Pepin the Short and Carloman waged a campaign to reduce Alamannia and in 746 Carloman began a final thrust to subdue the Alamannic nobility. Several thousand Alamanni noblemen were summarily arrested, tried, and executed for treason at a Council at Cannstatt. Thereafter, Alamanni was ruled by Franks and the only remaining native Alamannic nobility seems to have hailed from Alsace.

During the reign of Louis the Pious, there were tendencies to renewed independence in Alamannia, and the 830s were marked by bloody feuds between the Alamannic and Rhaetian nobility vying for dominion over the area. Following the Treaty of Verdun of 843, Alamannia became a province of East Francia, the kingdom of Louis the German, the precursor of the Kingdom of Germany. It was called a regnum in contemporary sources, though this does not necessarily mean that it was a kingdom or subkingdom. At times, however, it was.

It was granted to Charles the Bald in 829, though it is not certain whether he was recognised as duke or king. It was certainly a kingdom, including Alsace and Rhaetia, when it was granted to Charles the Fat in the division of East Francia in 876. Under Charles, Alammania became the centre of the Empire, but after his deposition, it found itself out of favour. Though ethnically singular, it was still plagued by Rhaetian-Alamannic feuds and fighting over the control of the Alammanic church.

Alamannia in the late 9th century, like Bavaria, Saxony, and Franconia, sought to unite itself under one duke, but it had considerably less success than either Saxony or Bavaria. Alammannia was one of the jüngeres Stammesherzogtum, one of the "younger" stem duchies, or tibal duchies, which formed the basis of the political organisation of East Francia after the collapse of the Carolingian dynasty in the late 9th and early 10th centuries. In the 10th century, no noble house of Alamannia succeeded in founding a ducal dynasty, as the Ottonians did in Saxony or the Liutpolding in Bavaria, though the Hunfridings came closest.

^in what is now Switzerland, the Alemannic areal has expanded during the high medieval period, with the Valser migration into the Alps, with the Zähringer and later the influence of Bern towards Upper Burgundy, and into Grisons as lower Raetia came under the rule of the Werdenberg counts.

Reuter, Timothy. Germany in the Early Middle Ages 800–1056. New York: Longman, 1991.